Welcome to our community and thanks for posting. Sorry to hear that you're having trouble treeing to register for a Mobile account online.
As you have already tried a different web browser, can we ask if you have deleted all cookies/caches and history and tried registering again?
You would need to use an obscure password that you have not used before. For more information about this check the link here. If you're still having issues, please come back to us and we can help you register from here for you.